1. Field of the Invention
The present invention relates to a disk driving device for driving a disk such as a compact disk or a CD-ROM.
2. Description of the Related Art
A description will be given of a conventional disk driving device of the above type, with reference to FIGS. 10 to 13.
In the conventional disk driving device in the figures, a spindle motor (not shown) causes rotation of a rotor yoke 11, which causes rotation of a turntable 13 having mounted thereto a rotary shaft 12 by press-fitting or the like. The turntable 13 is made of brass that is subjected to turning or the like. A cylindrical portion 13a is formed around the center portion of the turntable 13, with the aforementioned rotary shaft 12 press-fitted and secured to the center of the cylindrical portion 13a. A disk-shaped flange 13b is formed at the outer peripheral side of the cylindrical portion 13a, and has a flat surface having affixed thereto with an adhesive tape an anti-slipping sheet 14 serving as the disk-mounting surface.
The bottom surface of the turntable 13 is affixed to the rotor yoke 11. At the upper surface of the cylindrical portion 13a of the turntable 13 is formed a circular recess 13c having affixed therein an annular attraction magnet 15. A centering spring 16 for centering a disk D is supported in the recess 13c with the aforementioned attraction magnet 15.
As shown in FIGS. 10 and 12, the centering spring 16 is circular in appearance and is made of such material as synthetic resin. The centering spring 16 includes at the center side thereof a support portion 16a formed by bending a portion of the spring 16 downward, first tapering portions 16c formed at an end of its corresponding fulcrum 16b disposed at the outer peripheral side of its associated support portion 16a, and second tapering portions 16d formed continuously with their corresponding first tapering portions 16c. The first tapering portions 16c comprise a plurality of centering portions for centering a disk D. The second tapering portions 16c are sloped with a greater angle than the first tapering portions, with their free ends formed into a plurality of petal-like tongue pieces. Since the first and second tapering portions 16c and 16d are formed into a cantilever arrangement with the fulcra 16b as centers, the second tapering portions 16d used for centering the disk D are resiliently biased outwardly and obliquely upward in the direction of arrow A of FIG. 10.
A clamper 17 is disposed above the turntable 13 and the centering spring 16 in order to chuck the disk D placed at the flange 13b of the turntable 13, as shown in FIG. 11.
A description will now be given of the operation of the conventional disk driving device. As shown in FIG. 11, when a disk D is loaded into the conventional disk driving device, the peripheral edge of a center hole D1 of the disk D contacts the first and second tapering portions 16c and 16d of the center spring 16 having resiliency. While the second tapering portions 16d being resiliently biased in the direction of arrow A of FIG. 10 as mentioned above moves circularly on the fulcra 16b as centers, the disk D slides down along the first and second tapering portions 16c and 16d, as it presses the second tapering portions towards the cylindrical portion 13a of the turntable 13. Then, the disk D is centered at the first and second tapering portions 16c and 16d, and placed on the anti-slipping sheet 14 on the turntable 13.
At the same time that the disk D is centered, the clamper 17 which has been waiting above the turntable starts to move down. Then, the clamper 17 presses the surface of the disk D due to the attraction force of the attraction magnet 15, whereby the disk D is clamped by the turntable 13 and the clamper 17, thus completing the centering and chucking of the disk D.
Thereafter, when an electrical power with a predetermined phase is supplied to a drive coil of a spindle motor (not shown), the rotor yoke 11 rotates, causing integral rotation of the turntable 13 and the rotary shaft 12. Thus, since the disk D can rotate, while it is clamped by the clamper 17 and the turntable 13, information can be read out from or written onto the disk D.
In the conventional disk driving device, however, the first and second tapering portions 16c and 16d of the centering spring 16 are in a cantilever arrangement with the fulcra 16b as centers, so that the second tapering portions 16d used for centering the disk D are resiliently biased outward and obliquely upward in the direction of arrow A of FIG. 10. This produces a force that constantly tries to raise the disk D upward, which may cause the anti-slipping sheet 14 providing a disk-mounting surface of the turntable 13 to be raised upward, or the disk D to be loaded in an oblique state, when the disk D is loaded onto the centering spring 16. When the clamper 17 moves down, while the disk D remains raised from the disk-mounting surface of the turntable 16, or is loaded in an oblique state, the clamper 17 may scratch or deform the surface of the disk D, thereby preventing information to be properly read out from or written onto the disk D.
In the conventional centering spring 16, the distance from each fulcrum 16b to its corresponding second tapering portion 16d is short, thus increasing the load exerted on each fulcrum. When a load is repeatedly exerted onto each fulcrum 16b as a result of loading and unloading the disk, fatigue of the fulcrum 16b results, causing the disk D to break more often.
In addition, since the distance from the fulcrum 16b to the second tapering portion 16d is short, in order to produce a centering force, it is necessary that the first and second tapering portions 16c and 16d serving as arms have a large spring constant. Therefore, large variations result in the disk centering forces produced at the tapering portions due to dimensional variations, thereby reducing the disk centering precision, causing read errors to occur.
Further, since the first and second tapering portions 16c and 16d of the centering spring 16 comprise a plurality of petal-like tongue pieces, the area of contact between the second tapering portions 16d and the peripheral edge of the center hole D1 of the disk D becomes large, producing frictional resistance. Thus, when the disk D is loaded onto the centering spring 16, the disk D cannot slide smoothly, resulting in the problem that the disk D cannot be smoothly loaded onto the disk-mounting surface of the turntable 13.
Still further, since the front ends of the first and second tapering portions 16c and 16d of the centering spring 16 are free ends, it has been difficult to form the ends of the plurality of second tapering portions 16d along the same circumference due to manufacturing variations. Therefore, as shown in FIG. 13, when the disk D is loaded onto the centering spring 16, there were disk driving devices in which some of the plurality of second tapering portions 16d did not contact and thus were separated from the peripheral edge of the center hole D1 of the disk D. This has caused the disk D to be decentered or obliquely placed, or has prevented smooth loading of the disk D onto the disk-mounting surface of the turntable 13.